1.

Cos a /1-sin a = 1+tan a/2 / 1-tan a/2​

Answer»

Step-by-step EXPLANATION:We KNOW that CosA = 1 - Tan²A/2 / 1 + Tan²A/2                         SinA = 2TanA/2 / 1 + Tan²A/2CosA / 1 - SinA = [1 - Tan²A/2 / 1 + Tan²A/2] / 1 - [2TanA/2 / 1 + Tan²A/2]                  =  [1 - Tan²A/2 / 1 + Tan²A/2] / [1 + Tan²A/2 - 2TanA/2/1 + Tan²A/2]                  =  1 - Tan²A/2 / 1 + Tan²A/2 - 2TanA/2                  = 1 - Tan²A/2 / (1 - TanA/2)²                  = (1 + TanA/2)(1 - TanA/2) / (1 - TanA/2)²                  =  1 + TanA/2 / 1 - TanA/2.Hence PROVED.



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